1. Field of Invention
Exemplary aspects of the present invention relate to an image forming apparatus, and more particularly to an image forming apparatus including a contact-separate mechanism for contacting and separating a transferor to and from a toner image carrier.
2. Description of the Background
A related art image forming apparatus, such as a copying machine, a facsimile machine, a printer, or a multifunction printer having copying, printing, scanning, and facsimile functions, forms an electrostatic latent image on a photoconductor according to image data. The electrostatic latent image is developed with a developer (e.g., a toner) to form a toner image on the photoconductor. The toner image is transferred onto a recording medium (e.g., a sheet) and sent to a fixing unit. In the fixing unit, heat and pressure are applied to the sheet bearing the toner image to fix the toner image on the sheet.
The toner image formed on the photoconductor serving as a toner image carrier is directly transferred from the photoconductor onto a sheet as described above or indirectly transferred via another toner image carrier (i.e., an intermediate transfer member) onto a sheet. When the toner image is indirectly transferred via the intermediate transfer member, the toner image formed on the photoconductor is transferred onto the intermediate transfer member, and then further transferred from the intermediate transfer member onto the sheet. The toner image carrier opposes a transfer roller to form a transfer nip at which the toner image is transferred from the toner image carrier onto the sheet. Specifically, the toner image carrier and the transfer roller rotate to feed the sheet while the toner image is transferred onto the sheet.
The transfer roller contacts the toner image carrier when the transfer roller is not configured to separate from the toner image carrier while the sheet is not conveyed through the transfer nip. As a result, a residual toner remaining on the rotating toner image carrier may be adhered to the transfer roller. The adhered toner may be further adhered to the backside of a sheet conveyed to the transfer nip. When the toner image carrier and the transfer roller stop rotating for a substantial time period while the toner image carrier contacts the transfer roller, the toner image carrier and the transfer roller may be deformed.
To address the above-described problems, the related art image forming apparatus can include a contact-separate mechanism for contacting and separating the transfer roller to and from the toner image carrier as needed. For example, one example image forming apparatus includes a contact-separate mechanism for contacting and separating a transfer roller to and from an intermediate transfer belt (i.e., the toner image carrier). The example image forming apparatus further includes an upstream guide to guide a sheet to the transfer nip. The upstream guide is disposed on an upstream side from the transfer nip formed between the intermediate transfer belt and the transfer roller relative to a sheet conveyance direction. However, the upstream guide may be unstably positioned with respect to the transfer roller when only the transfer roller is moved to contact and separate to and from the intermediate transfer belt. As a result, the sheet may not be stably conveyed and may be jammed.
To address the above-described problem in the example image forming apparatus, the upstream guide and the transfer roller are moved together so that the transfer roller contacts and separates to and from the intermediate transfer belt. Thus, the position of the upstream guide with respect to the transfer roller is fixed even when the transfer roller is moved to contact and separate to and from the intermediate transfer belt. As a result, the sheet can be stably conveyed on the upstream side from the transfer nip relative to the sheet conveyance direction, thereby preventing the sheet from being jammed.
In the example image forming apparatus, a downstream guide is disposed on a downstream side from the transfer nip relative to the sheet conveyance direction to guide the sheet toward a fixing unit. However, the position of the downstream guide with respect to the transfer roller is not fixed. Therefore, the sheet may be unstably conveyed on the downstream side from the transfer nip relative to the sheet conveyance direction and may be jammed. The sheet, which has passed the transfer nip, bears an unfixed toner image. When the sheet is jammed on the downstream side from the transfer nip relative to the sheet conveyance direction, toner particles forming the unfixed toner image may scatter from the sheet and thereby may stain the interior of the image forming apparatus.